Antenna combined with magnetic coupling core



July 17, 1956 G. MOUNTJOY 2,755,468

ANTENNA COMBINED WITH MAGNETIC COUPLING CORE Filed April 2, 1955 2 Sheets-Sheet l FIG.2

IN V EN TOR.

GARRARD MOUNTJOY HIS AGENT July 17, 1956 G. MOUNTJOY 2,755,463

ANTENNA COMBINED WITH MAGNETIC COUPLING CORE Filed April 2, 1953 2 Sheets-Sheet 2 FIG. 3

INVENTOR.

GARRARD MOUNTJOY HIS'AGENT United States atent O ANTENNA COMBINED WITH MAGNETIC COUPLING CORE Garrard Mountjoy, Canadaigua, N. Y., assignor, by mesne assignments, to General Dynamics Corporation, a corporation of Delaware Application April 2, 1953, Serial No. 346,354

'12 Claims. (Cl. 343-450) My invention relates to antennas, and more particularly to directional antennas.

It is an object of my invention to provide a directional antenna which requires no shielding.

It is also an object of my invention to provide a high impedance loop antenna without commutation or slip rings.

It is a further object of my invention to provide a directional antenna which is capable of operating over a wide range of frequencies.

It is yet another object of my invention to provide a directional antenna which is compact.

In general, I accomplish these and other objects of my invention by providing a rotatable magnetic core having signal pickup and signal transfer portions. These portions are preferably oriented substantially at right angles to each other. A stationary coil is wound coaxially around the signal transfer portion with suflicient clearance to permit clear rotation. When placed in the field of a transmitter, energy is picked up by the signal pickup portion of the rotatable magnetic core and is transferred to the signal transfer portion. A voltage is thus induced in the stationary coil. The signal strength picked up depends upon the orientation of the signal pickup portion. By rotating the signal transfer portion about a vertical axis, the signal pickup portion is made to extend radially outward from the central axis of the stationary coil in a horizontal plane. As the signal pickup portion is rotated in the horizontal plane, a signal strength vector pattern is swept out.

Further objects and advantages of my invention Will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to the accompanying drawing in which Fig. 1 shows a preferred embodiment of my invention;

Fig. 2 shows a signal strength vector pattern obtained with the arrangement of Fig. 1; and

Fig. 3 shows a second embodiment of my invention which is particularly adapted to cover a wide range of frequencies.

Referring now to Fig. 1, there is shown a rotatable magnetic core 1 which has signal pickup, or end, portions 2 and 3, and signal transfer, or center, portion 4. The center axes of both ends and center portions are preferably disposed in uniplanar relationship, with the axes of the end portions extending radially away from the axis of the center portion in directions substantially 180 apart.

Core 1 is preferably oriented for free rotation about a vertical axis 55 which passes through the center of center portion 4. I have shown core 1 arranged to be rotated by means of a stub axle 6. Stub axle 6 may be supported by any conventional bearing means. The latter is not shown, since the nature thereof forms no part 2,755,458 Patented .luly 17, 1956 ice of my invention and in any event may be of any type well known in the mechanical arts which is capable of performing the desired function.

A stationary coil 7 is disposed in inductive relationship to core 1, preferably by being wound coaxially around center portion 4 of core 1. Coil 7 is spaced from core 1 to permit free rotational movement of the latter. It is one of the advantages of my invention that coil 7 may have an appreciable number of turns, thus affording a high-inductance winding. A variable capacitor 8 may have its terminals connected across coil 7 to form a parallel-tuned circuit therewith. Since coil 7 may have a high-inductance, due to the absence of slip rings which are frequently found in directional antennas of the rotating coil type, the amount of capacitance in capacitor 8 required to tune to a given frequency may be relatively low.

Core 1 is preferably made of finely divided magnetic particles. Powdered or carbonyl iron particles are satisfactory if theparticle size is chosen in accordance with the frequency range it is desired to cover.

The voltage appearing across the leads of the tuned circuit comprising coil 7 and capacitor 8 may be utilized in any desired manner, a general indication being given in Fig. l by block 9. Block 9 may represent a conventional radio receiver, the input terminals 10 and 11 of which may, for example, lead to a grid circuit of an input vacuum tube. However, block 9 may represent other suitable apparatus.

A signal strength vector pattern obtainable with the arrangement of Fig. 1 is shown in Fig, 2. A transmitter field is assumed to have the direction shown by arrow 12. Axis 5-5 is perpendicular to the plane of the drawing. A polar plot about axis 5 of signal strength versus antenna angle in this situation produces the figure-8 pattern shown. It may be noted that a single end portion may be employed instead of the two end portions, 2. and 3; in that case, with somewhat reduced signal input efficiency.

A figure of merit for directional antennas may be defined as the ratio of output voltage divided by field strength. With pickup portions 2 and 3 about four inches long, a figure of merit has been obtained for the embodiment of Fig. 1 operating in the AM broadcast band (550-1600 kc./s.) of about 0.5.

Because of the magnetic nature of core 1 and because coil 7 is oriented with its axis vertical, electrostatic pickup is at a minimum. Electrostatic shielding is therefore not necessary.

Fig. 3 shows an embodiment of my invention which is adapted to cover a wide range of frequencies in a relatively small volume. Here a plurality of directional antenna elements, each preferably having substantially the configuration of Fig. 1, are oriented with the end portions and central portions of each core in uniplanar relationship. The cores are coupled together for unitary Iotation, as by means of shank 14 between cores 15 and 16 and shank 17 between cores 16 and 18. The cores may be secured to the shanks by any convenient means (not shown, since the application of such means is well within the skill of the artisan). The resulting unitary structure may be rotated by stub axle 19, which is supported by any suitable bearing means, a wide variety of which are also well known to the artisan. Tuned circuits 20, 21 and 22, which are respectively coupled to cores 15, 16 and 18, are individually proportioned for the particular range of frequencies it is desired to cover. The characteristics of the core material in each directional antenna element are likewise chosen for suitability to the particular frequency range involved.

The output tuned circuits 20, 21 and 22 may be respectively amplified by amplifiers 23, 24 and 25. In accordance with conventional practice, low potential output terminals 26, 27 and 23 of amplifiers 23 to 25, respectively, may be connected in common. The high potential output terminals 29, 3t and 31 of amplifiers 23 to 25 are respectively led to contacts 32, 33 and 34 of switch 35. Contact arm 36, of switch 35 may be placed on any of contacts 32-34 to furnish to a utilization circuit, indicated schematically and generally by block 37, the voltages developed in any one of amplifiers 23 to 25 by proper setting of switch arm 36.

While I have shown and described my invention as applied to a specific embodiment thereof, other modifications will readily occur to those skilled in the art. I do not, therefore, desire my invention to be limited to the specific arrangement shown and described, and I intend in the appended claims to cover all modifications within the spirit and scope of my invention.

What I claim is:

1. A directional antenna, comprising the combination of a rotatable magnetic core having signal pickup and signal transfer portions angularly oriented to each other, and a stationary coil disposed in inductive relationship to said signal transfer portion and spaced therefrom for free rotational movement of said core relative to said coil.

2. The combination of claim 1 in which said core comprises finely divided magnetic particles.

3. The combination of claim 1 in which said signal pickup and signal transfer portions are oriented substantially at right angles relative to each other.

4. A directional antenna, comprising the combination of a rotatable magnetic core having a central portion for signal transfer and end portions for signal pickup, said end portions being located at opposite ends of said central portion and being angularly oriented relative to said central portion, and a stationary coil wound coaxially around said central portion and spaced therefrom for rotatable movement of said core relative to said coil.

5. The combination of claim 4 in which said core comprises finely divided magnetic particles.

6. The combination of claim 4 in which said central portion is oriented substantially at right angles of said end portion.

7. The combination of claim 6 in which said end portions and said central portion have central axes lying in the same plane, said plane also including the axis of said coil.

8. The combination of claim 7 in which said axes of said end portions extend radially away from said axis of said central portion in directions substantially apart.

9. In a wide-frequency-range directional antenna, the

combination of a plurality of directional antenna 61.

merits, each said element comprising a rotatable magnetic core having a central portion for signal transfer and end portions for signal pickups, said end portions being located at opposite ends of said central portion and being angularly oriented relative to said central portion, and a stationary coil wound coaxially around said central portion and spaced therefrom for free rotational movement of said core relative to said coil; means coupling said cores for unitary rotation with all said end portions and said central portions in uniplanar relationship; and means for selectively obtaining said output from said coils of said elements.

10. The combination of claim 9 in which said corescomprise finely divided magnetic particles.

11. A combination of claim 9 in which, in each said element, said end positions are oriented substantially at right angles to said central portion.

12. The combination of claim 11 in which, in each said element, said end portions extend radially away from said axis of said central portion in directions substantially 180" apart.

References Cited in the file of this patent UNITED STATES PATENTS 2 ,156,055 Holsten Apr. 25, 1939 2,413,951 Carter Ian. 7, 1947 2,581,348 Bailey Jan. 8, 1952 

